Electron discharge apparatus



May 30, 1939. T 2,160,796

ELECTRON D1 5 CHARGE APPARATUS Filed Nov. 20, 1956 3 Sheets-Sheet 1gym/70R By TEAL 0 m 6.14mi

A TTORNEY May 30, 1939. TEAL 2,160,796

ELECTRON DISCHARGE APPARATUS Filed Nov. 20, 1936 3 Sheets-Sheet'Z FIG 7W225?" INVENTOR By GK TEAL ATTORNEY May 30, 1939. G. KJTEAL ELECTRONDISCHARGE APPARATUS Filed Nov. 20, 1936 5 Sheets-Sheet 3 lNVENTOR GKTEAL v A TTORNEV Patented May 30, 1939 UNITED STATES PATENT OFFICE BellTelephone Laboratories,

Incorporated,

New York,"N. Y.,. acorporation of New York Application November 20,1936, .Serial .No.. 111,808

' 11 claims. (01150-166 in the 'device,.are directed to and impinge uponThis-invention relates to; electron discharge apparatus and moreparticularly tosuchtapparatus adapted to amplify high. frequencyimpulsesaand including electron. discharge devices having secondaryelectron emitting electrodes.

Oneobject of this invention is torenable. the economic, efficient andfacile attainment: oflarge and high .fi'delity amplificationof highfrequency impulses.

Another object of this invention is to enable the accuratedeterminationoi the characteristics of amplifiersutilizing electrondischarge devices.

Another object of this invention is to obtain) a high. signal to "noiseratio in electronie'amplifiers.

Still anotherobject of this; invention is to simplify the structure ofmulti-stage electron discharge apparatus and to reduce the number-ofcomponent parts thereof requisite to produces; high degree ofamplification. I

Aiurther object of this invention is to expedite the fabrication ofelectron discharge devicesthaving; a. multiplicity of electrodes;

In one illustrative embodiment of? this invention, electron dischargeapparatus comprises anv electron discharge device including a primarycathode, a collector electrode or anode, and a plurality of auxiliary orsecondary cathodes disposed between the primary cathodeand'the'collector electrode. The variouscathodes may be channel shaped,disposed-edge to edge and in alignment andhave one, preferably theinner, surface, or both surfaces, thereoi'coat'ed-with a materialcapable of producing copious emission of electrones:

Each rof the 'secondary cathodes is operated at emitting surfacethereof, the electrons emitted,

thereby are directed. to and impinge upon the first of the. secondarycathodes, under the influence of the magnetic field and the potential.upon this secondary cathode. As a result, secondary electrons arereleasedfrom the first secondary cathode and these electrons under theinfluence of the magnetic and'electro-staticfields: extant the nextsecondary cathode to cause the release of secondary electrons therefrom.This action is. repeated. to the: last secondary cathode, that is, theone furthest removed from the primary cathode, and theelectrons:releasedtherefrom are attracted to the collector electrode oranode and constitute an available output current for a utilizationcircuit connected, for example, to the pri-- mary cathode and thecollector electrode.

Inasmuch as the several secondary cathodes have suriaces'coated withamaterial having good secondary electron emitting properties, eachprimary or secondary electron impinging thereon will cause the. releaseof a plurality of secondary electrons. Hence, alargc electronmultiplication occurs between the primary cathode and the collectorelectrode so that in: effect: the signal corresponding to the activatingsource for the primary-cathode is greatly amplified as represented bythe. electron flow to. the collector electrode-or anode. Variations inthe intensity of the activating source will result in correspondingvariations-in-theelectron current to the collector electrode. oranodeandhence in the output current of the device.

The invention and the. various: featuresthereof will be understood moreclearly and fully from the following detailed description with referenceto the accompanying drawings, in which Fig. 1 is a view in; perspectiveof electron dis charge apparatus illustrative.- of. one embodiment ofthis invention, a portion of the enclosing vessel of the electrondischarge device being broken away to show the. internal structure moreclearly;

Fig. 2 is a top view, partly"incross-section, of the apparatus shown inFig. 1, the magnet being modified to show another formthereof;

Fig. 3 is anenlarged, partly exploded detail View in perspectiveillustrating. structuraldet'ails of the electron discharge device shownin Fig..l; Fig.4 is an elevational View in perspective of an electrondischarge device illustrative oi another embodiment of this invention;

Fig. 5 is a view'in cross-section of the cathode structure of thedevice'shown in Fig. 4;

Fig. 6'is' an enlarged; detail View in perspective and partly explodedillustrating the association of the cathodes and the supports thereforin the device shown in Fig. 4; and:

Fig. 7 isa circuit diagram of space discharge apparatus constructed inaccordance with this invention.

Referring. now to the drawings, the apparatus shown in Fig. 1 includesan electron discharge device comprising an elongated cylindricalenclosing vessel 10 having a stem II at one end provided with anintermediate, integral annular flange l2. A unitary electrode assemblyis mounted upon the stem H and includes a primary cathode [3, acollector electrode or anode [4, a screen or shield electrode l5 and aplurality of auxiliary or secondary cathodes IE to I6 inclusive.

The several electrodes are mounted upon a supporting structurecomprising a split metallic band or collar I! clamped about the stem II,a plurality, for example four, of rigid supports 18 extending from theband or collar l1, and a pair of grooved or channel shaped cross-piecesl9 afiixed to the supports I8. Each of the crosspieces [9 clamps andsecurely holds an elongated insulating member or upright 20, for examplea strip of mica, having a plurality of fingers 2|. The insulatingmembers 20 preferably are mounted parallel to each other and aremaintained in proper spaced relation by cross-members or braces 22,which also may be strips of mica, having slots in which the insulatingmembers are frictionally fitted.

As shown more clearly in Figs. 2 and 3, each of the cathodes is channelshaped, for example in the form of a rectangulated U, and the sides orarms 23 thereof are bent about and grasp corresponding of the fingers 2|on the insulating uprights 23. The arms 23 may be indented as indicatedat 24 to lock the cathodes to the uprights 20. Each cathode has securedthereto a metallic clip 25, which serves as a terminal lug to which aleading-in conductor may be afiixed. As indicated at 2'6, the clips 25may be indented to lock them to the arms 23 of the cathodes. The primaryand secondary or auxiliary cathodes are mounted in alignment withcorresponding surfaces thereof in common planes. The spacing betweenjuxtaposed edges of the cathodes may be of the order of inch.

The several cathodes may be formed of strips of silver or copper havingportions thereof, preferably only the surface .of the portion betweenthe arms 23, treated to render them capable of copious electronemission. For example, these portions may be oxidized, as by a highpotential discharge, and treated with caesium to provide a coating orsurface containing caesium oxide, silver and some free caesium.

The anode or collector electrode I 4, as shown clearly in Fig. 3, is ofthe same form as the cathodes and has its arms 21 bent around and lockedto the insulating uprights 20, one of the arms having afiixed thereto aterminal clip 28 similar to the clips 25. The base of the anodepreferably is disposed parallel to the bases of the cathodes andslightly displaced from the common plane thereof.

The shield or screen electrode I 5 includes a fiat relatively coarsemesh portion supported by metallic clips 29 grasping the uprights 20 andlocked thereto by indentations 30. Preferably the mesh portion is ofsubstantially the same area as the base of the anode or collectorelectrode l4 and is disposed substantially coplanar with the bases ofthe primary and secondary cathodes.

Disposed about the stem end of the enclosing vessel and frictionallymounted thereon is an insulating base 3| which carries a plurality ofterminal members 32, one for each of the electrodes of the device.Leading-in conductors 33 are connected to the terminal members 32,extend inwardly of the stem II, and are sealed in uniform space relationin the annular flange l2. Suitable conductors 34 are affixed at one endto the projecting ends of the leading-in conductors 33 and at the otherend to the clips 25, 28 and 29 on the cathodes, anode and screenelectrode, respectively. Preferably all but the ends of the conductors34 are encased in insulating material, such for example, as glasssleeves 35.

The electron discharge device heretofore described may be mounted on acarrier which includes a rigid L-shaped support 36 and resilient bowedarms 31 mounted on the support 36 and adapted to grasp the enclosingvessel Ill. The lower arm of the support 36 is fitted slidably in atrack or groove 38 in a suitable base 39 and has afiixed thereto afinger piece or bracket 49, which is pivoted at one end on the base 39as by a screw 4|.

Mounted upon the base 39, as by bolts 42, is a permanent magnetstructure which may be composed of a plurality of strongly magnetizedhorseshoe magnets 43. The several magnets may be clamped togetherbetween brackets 44 drawn toward each other by a wing nut 45 and spring46 mounted on a bolt 41 extending from the base 39.

The magnet structure produces an intense magnetic field at substantiallyright angles to the longitudinal axis of the electron discharge deviceand substantially parallel to the bases of the cathodes l3 and I6 andimmediately adjacent the electron emitting surfaces thereof. Theposition of the device relative to the magnet may be adjusted by meansof the finger piece 40 so that the emitting surfaces of the cathodes arein the strongest or most intense portion of the magnetic field. In orderto obtain sharper focussing of the electron streams, the magnet may haveits poles so related that a curved magnetic field is produced adjacentthe electrodes. For example, the poles may have chamfered faces as shownin Fig. 2. Also, as described more fully in the copending application ofWilliam A. Knoop, Serial No. 111,796, filed November 20, 1936, themagnet may be so constructed that the magnetic field is of greatestintensity in the vicinity of the primary cathode and decreases uniformlyin intensity to in the vicinity of the collector electrode. As shown inFig. 1, the magnet preferably extends somewhat above the anode !4 andslightly beyond the primary cathode I3.

During operation of the apparatus, the secondary cathodes T6 areoperated at positive potentials with respect to the primary cathode, thepotential upon each secondary cathode being higher than that upon thenext preceding one with reference to the primary cathode. For example,the first secondary cathode I6 may be operated at of the order of 135volts positive with respect to the primary cathode l3, the secondarycathode 16 at of the order of 270 volts positive, and each succeedingsecondary cathode at of the order of 135 volts positive higher than thenext preceding one so that the secondary cathode I6 is of the order of1080 volts positive with respect to the cathode l3. The shield or screenelectrode l5 may be operated at a potential of the order of 135 voltspositive with respect to the secondary cathode Hi and the collectorelectrode or anode I4 may be operated at a potential of the order of 250volts positive with respect to the secondary cathode I6 As shown in Fig.7, the potentials for a number of the secondary cathodes l6 may beobtained from a potentiometer 41, which may be supplied from a suitablesource such as a rectiher 48. Because of the heavycurrent drain, thepotentials: for r the secondary cathodes, for' exam:- pied-G and 16and'for the; screen; 15 andi-vanode or: collector: electrode k4:preferably are obtained fromseparate-sources such-as-batteries 50 conenectedin series as shown.

The-primary cathode l=3-may-beenergized by a beamof:lightrfoc.ussed:upon the activated portion' thereof through a lens.51: andv emanating fromwa=suitable= source, such as-a lamp '52, theintensity 4 of: the light beam being variable" as by a suitable film 60.Under the-=influence of-such awlight: beam,: the primarycathode I 3emitsielectrons-"and-theseelectrons, underzthe influence of the:magnetic-field. in: the vicinity of the cathode I 3 and theelectrostatic fields obtainingbecause of the positive potentialsupon-the other electrodes oh the device, areattracted to: and: impingeupon. the secondary :or auxiliary cathode I 6 The velocity of theseimpinging electrons is relatively high.- so that: secondary electrons:are .released :from %the activated or coated portion: of the-cathode HiTheintensity of 'thissecondary electron :emission will 'be dependentprimarily upon the character of the coating ,upo-n. the'cathode 1'6 and.the potentiakof this cathode with respectto theprimary cathode. Forexample, if the emitting surface be of: caesium treated silver oxide,'as :heretofore described, and the cathode I6 be operated at a potentialof the order of 135 volts'positive withrespect to'thecathode .Ii3, thesecondary GIGGETOI'L': stream from the cathode IE willbe approximately 3to 7 times as great 'as the, primary 'electronsemanating from theprimary cathode 1 3-.v Ineffect, therefore, the'primaryrelectron streamis multipliedand as aresult an amplification! of the signal:corresponding to the light beam energizing theiprimary -cathode obtains.

The secondary electrons emanating from the cathode- $6 undertheiinfiuence. of: the magnetic and the electrostaticfields extantadjacent this cathode, are directed towardandtimpinge upon the-secondarycathode 1 6 These electrons :are adsorbed bythe/cathode:tii 'and produce'a'copious: emission-of other-secondary'electronsfrom' this cathode.Foreach; electron impinging upon the-cathode M6 aplurality-of secondaryelectrons-are released therefrom-so that effectively a The secondaryelectrons emanating from the cathode i are directed to and adsorbed bythe anode or collector electrode l4 and constitute the output current ofthe device. This current may be employed in any suitable utilizationcircuit associated with the anode or collector as shown in Fig. 7.

The shield electrode l5 serves to screen the end cathode Hi from theanode or collector electrode l4 and thereby presents undesired reactionof variations in the anode or collector potential upon the cathode l6and hence minimizes distortion in the output current of the device.

Itih-as been found-thatthe operating characteristics of the device,principally the relation between theoutput current and the-=intensity ofthe light beam energizing the cathode I3, are materially dependent uponvthe design of thesecondary cathodesdit. For mostpurposesiit isdesirablethat the output current-lightzbeam.intensitycharacteristic besubstantiallylinear throughout the output current range correspondingtothe'range of. intensitiesof'the light beam'played upon the primarycathode 13. This desirable relationship may be obtained by making thewidth of the secondarycathodes l-6 approximately 5 times-the depththereof and the longer dimension approximately twice the shorterdimension. For example, it has been found that if the secondary cathodesare approximately 1.2 centimeters by approximately 0.6 centimeter and0.25 centimeter deepwand are spaced-of the order of 0.1 25-rcentimeter,.the output current will: vary substantially linearly with .theintensity of the light beamover arrange f.rom.-substanti-ally zerotoatleastldmilliamperes. If non-linear char acteristics-aredesired, they-.may be-obtained by increasing the depth of the secondary cathodes.

It maybe pointersloutalso that the channel shaped form-of theseveralcathodes results in reduction of thelateral dispersion "of thepri mary andusecondary' electron. streams,,-so that concentratedelectron beams obtain and a high operating. efficiency results.

This desirable concentration of the electron beams may beenhanced'bydisposing the'secondary cathodes 16 anduthe primary cathode 1 i3 atasmall angle, for example of the order of. twenty degrees, tothe-:longitudinal axis of the electrode structure-as shown'in'Figs. 4; 5and 6-. The electronidischarge device shown in these figuresissubstantiallythesame as that'show-n in Fig. 1', except that thecathodes-|=3 and 16- are tilted and-the fingersdl: on-the-insulatingmembersillare .provided with edges '53? sloping -at'the same angle asthe cathodes. Thedevice 'may be mounted in. the samemanner as. thedevice shown in Fig. 1 and connected in a'circuitsuch as shown inEig.'7.

Although specificembodiments of this invention havebeensshown'anddescribed, it will: be understood, of course, that these embodiments aremerely-illustrative ofthis invention and'that various modifications, maybe made'therein. For example, although eight secondary cathodesare shownin the-deviceof Fig. 1 and nine in=the device shown inrFig. 4, a greateror lesser number may be employed. Furthermore, although the primarycathodes i3 are disclosed as of the photoelectric type they may be ofothertypes, for example, thermionic, directly or indirectly heatectand aseparate grid or control electrode maybe utilized .for modulating theprimaryelectron;str.eam1f-rom the primary cathode l3 to. the firstsecondary cathode'tfi in: accordance withva signal to be amplified.Moreover, in modifications of the embodiments heretofore described, theanode or collector electrode l4 may be disposed with its electronreceiving surface at substantially right angles to the axis of alignmentof the cathodes and both surfaces of the primary and secondary cathodesmay be provided with a layer or coating of electron emitting materials.Similarly, the shield or screen electrode l5 may be disposed at rightangles to the axis of alignment of the cathodes. Two screen electrodesmay be provided adjacent opposite surfaces of the anode or collectorelectrode l4 when both surfaces of the cathodes are sensitized and theanode or collector electrode is substantially parallel to the cathodes.Other modifications may occur to those skilled in the art without,however, departing from the scope and spirit of this invention asdefined in the appended claims.

What is claimed is:

1. Electron discharge apparatus comprising a primary cathode, acollector electrode, a plurality of secondary cathodes between saidprimary cathode and said collector electrode, said secondary cathodeshaving electron focussing flanges electrically connected thereto andforming channels constituting a path for the electron streams, andmounted end to end and in alignment with one another, and a coating ofelectron emissive material upon the inner surface of said channels.

2. Electron discharge apparatus comprising an enclosing vessel, a pairof insulating uprights mounted in said vessel, a primary cathode, acollector electrode, a plurality of secondary cathodes disposed betweensaid primary cathode and said collector electrode and in alignment withone another, and having electron focussing flanges electricallyconnected thereto and forming channels constituting a path for theelectron streams, said flanges bent about and grasping said uprights,and an electron emissive coating upon the inner surface of saidchannels.

3. Electron discharge apparatus comprising a primary cathode, acollector electrode and a plurality of aligned secondary cathodesbetween said primary cathode and said collector electrode, saidsecondary cathodes having electron focussing arms electrically connectedthereto and parallel to the axis of alignment of said secondary cathodesforming channels of a depth less than the width thereof, the width beingdetermined by the spacing of said arms, said channels constituting apath for the electron streams, and the inner surface of said channelshaving thereon a coating of electron emissive material.

4. Electron discharge apparatus comprising a primary cathode, acollector electrode, and a plurality of secondary cathodes disposedbetween said primary cathode and said collector electrode, and metallicmeans electrically integral with said secondary cathodes and at oppositesides thereof for laterally confining the electron streams from saidprimary and secondary cathodes.

5. Electron discharge apparatus comprising a primary cathode, acollector electrode, and a plurality of auxiliary electrodes betweensaid cathode and said collector electrode, said auxiliary electrodeshaving secondary electron emitting portions in alignment with oneanother and said cathode. and having integral portions on opposite sidesof the axis of alignment of said emitting portions for laterallyconfining the electron streams emanating from said primary cathode andsaid portions to aligned paths.

6. Electron discharge apparatus comprising a primary cathode having aplane emitting portion, a collector electrode, a plurality of secondarycathodes between said primary cathode and said collector electrodehaving electron emitting portions disposed edge to edge andsubstantially coplanar with said plane emitting portion and in alignmenttherewith, and members at opposite sides of said emitting portions andelectrically integral therewith for laterally confining the electronsemanating from said emitting portions to restricted paths.

'7. An electron multiplier comprising a primary cathode, a collectorelectrode, and a plurality of similar, equally spaced, successivelymounted secondary cathodes between said primary cathode and saidcollector electrode, said secondary cathodes having channel-shapedemissive portions, the inner surface of which is electron emissive.

8. Electron discharge apparatus comprising a primary cathode, acollector electrode, and a secondary cathode between said primarycathode and said collector electrode and in alignment therewith, saidsecondary cathode having electron focussing flanges electricallyconnected thereto forming a channel constituting a path for the electronstream, the inner surface of said channel being exposed and secondaryelectron emissive.

9. Electron discharge apparatus comprising a primary cathode, acollector electrode, a plurality of secondary cathodes between saidprimary cathode and said collector electrode, said secondary cathodeshaving channel-shaped portions disposed edge to edge and withcorresponding surfaces thereof substantially coplanar, the innersurfaces of said portions being exposed, and a secondary electronemissive coating upon said inner surfaces.

10. Electron discharge apparatus comprising a primary cathode, acollector electrode, a plurality of secondary cathodes between saidprimary cathode and said collector electrode, said secondary cathodeshaving rectangulated U-shaped portions disposed edge to edge and withcorresponding surfaces thereof in common planes, the inner surfaces ofsaid portions being exposed, and

a secondary electron emissive coating upon said inner surfaces.

11. Electron discharge apparatus comprising a primary cathode, acollector electrode, and a plurality of substantially rectangulatedU-shaped secondary cathodes between said primary cathode and saidcollector electrode, said secondary cathodes having their inner surfacesexposed and adapted to emit secondary electrons, and. the arms of eachof said secondary cathodes being spaced from each other a distancegreater than the dimension of said arms at right angles to the bases ofsaid secondary cathodes.

GORDON K. TEAL.

